In so many departments this season, Manchester United have smacked of inconsistency, blowing hot and cold not only from one game to another, but in two halves of the same game.
Nowhere was that more present than Saturday's victory at the London Stadium, where, for the second week running, Ole Gunnar Solskjaer's side had to overturn a half-time deficit to come away with three points.
Just as they did at Southampton, where defeat was similarly starring United in the face, Solskjaer's substitutes delivered, transforming a contest they had no right to transform after his starting XI were left off the hook by poor Hammers finishing.
It begged the question how many more times Manchester United would get away with such an abject first-half display, and why the scintillating attacking play of the second period couldn't be produced before they fell behind.
But while Solskjaer hunts for answers to both of those questions, the United boss can bask in the glory of one area where his team are consistent, very consistent, and that's winning away from home.
Not only did the 3-1 victory over West Ham extend Manchester United's away league winning streak to nine games, it confirmed a fifth away win from their opening five this season for the first time since 1985/86.
Manchester United's quality is unquestionable but the same cannot be said for the consistency needed to take the team back to the very top. This, it would appear, remains Solskjaer's biggest challenge, dare I say it, and one of few obstacles standing between them and title candidacy.
There will more emphatic victories for Chelsea than this one against Leeds - secured in stoppage time by Christian Pulisic. But this 3-1 win for Frank Lampard's side, on the day that supporters returned to Stamford Bridge, was full of signs that this is a title challenge that can survive the stresses of winter. Chelsea top the table and are showing some real steel.
They had to come from behind after Patrick Bamford's early goal. There was then the loss of Hakim Ziyech through injury. But these tests were overcome and what was most encouraging was the manner in which Chelsea saw out the game as Leeds pushed - everyone working, defending from the front, determined to secure the points.
There were more than enough chances in the game to have seen Leeds off far sooner. Chelsea's tally of 23 shots is a season high for them as well as the most that their opponents have faced in a game. An expected-goals total of 4.07 is the highest of any team in a Premier League game this season. Chelsea have attacking options in abundance.
Olivier Giroud's recent impact only adds to that depth, his equaliser here adding to his four goals against Sevilla in midweek. His link up with Timo Werner shows promise - even if the German was inexplicably unable to finish at the far post after Giroud's flick on.
There was no goal from that corner but Kurt Zouma's second-half header means that Chelsea have scored more goals from corners than any other Premier League team this season. This is a team that can hurt their opponents in so many different ways.
With Bamford's goal only the third that Chelsea have conceded in their last 11 games in all competitions, this is the sort of form at both ends of the pitch that brings success. The summer investment was significant but 16 games without defeat tells its own tale. Chelsea are showing the organisation, the squad depth and the quality to compete for the title.
It's now four starts and four clean sheets for John Stones since returning to the Manchester City defence in November. It's easy to forget that the England international only started four games for City in a 10-month period before he was given a chance against Olympiakos in the Champions League a month ago.
Early signs are that Stones might just be back to his best. Yes, Ederson could have played in his club's suit and popped out to do his Christmas shopping such was the lack of adventure from Fulham, but Stones answered every call whether it was his passing out from the back or stopping the dangerous runs of Ademola Lookman.
"The manager demands and expects a lot, we're all fighting for all places," Stones said. "We have to take our chance when we get one. It's good, healthy competition."
It could have all gone pear shaped for him, though. Stones' recent good form has been a huge positive for City but the centre-back had a moment to forget when he failed to notice Ederson was away from his goal as he hit a back pass. The Brazilian had no chance of retrieving the situation but, fortunately for Stones, the ball rolled wide.
It was just a reminder of why perhaps in the long term Aymeric Laporte still has the reliability factor to be Ruben Dias' partner when it really matters.
If Everton's draw at Burnley taught us anything, it's that Carlo Ancelotti has to stick with his preferred 4-3-3 formation. That's where his players flourish and how he can get the best out of them.
Initially, Ancelotti had once again lined up with three centre backs and two wing-backs, which was surprising after its ineffectiveness against Leeds last weekend. As the manager admitted before the trip to Turf Moor, this was borne out of necessity after injuries to full-backs Seamus Coleman and Lucas Digne.
But Everton started the game incredibly poorly with their new-look formation. Allan and Abdoulaye Doucoure - so often the consistent performers - looked bereft of confidence. They gave the ball away time and again in the opening half an hour and Allan was punished for his error when Burnley took the lead inside three minutes.
And although Ancelotti will not welcome another injury, Fabian Delph's hamstring strain paved the way for a switch back to 4-3-3, with Alex Iwobi and Ben Godfrey playing at right and left-back respectively. Everton looked much more assured from then on, Doucoure making those driving forward runs they paid for in the summer and the makeshift full-backs did well.
While Iwobi and Godfrey plugged a gap on Saturday, they are by no means the answer to Everton's issues. Let's not forget, Everton have a talented young left-back in Niels Nkounkou, who has impressed in the Carabao Cup, and Seamus Coleman will hopefully return soon. One thing is for sure, though - 4-3-3 is the way forward for this team.
David Moyes pointed at a dubious refereeing decision for West Ham's collapse against Manchester United, but there was an all too familiar feel to the Hammers' latest setback on their big return to the London Stadium.
For 45 minutes the script looked to be going just as West Ham would have wanted it on the momentous day they opened the gates of their stadium to supporters for the first time since February, with Tomas Soucek giving them a deserved half-time lead.
For all the positives of the first period, West Ham should have scored more, and as time passed you just wondered whether they would live to rue the host of missed chances afforded to them by the porous Manchester United defence.
That, coupled with a willingness to sit back early in the second period, gave Manchester United a glimmer of hope, which they seized to devastating effect.
The Hammers were aggrieved when Paul Pogba's spectacular strike was allowed to stand, despite huge calls that it had travelled out of play in the build-up, and they were still reeling when Mason Greenwood put the visitors ahead in the space of three second-half minutes.
By the time Marcus Rashford added a third, West Ham's hopes were over, and their claim to an unwanted record was confirmed. No Premier League side have dropped more points from a winning position than the Hammers' tally of 19 in 2020.